Abstract: A method and apparatus for improving the fatigue and stress corrosion cracking performance of irregular surfaces, such as welds assemblies of components, using a positioning system, such as a robotic or CNC machine, to position a tool head for inducing compression along and into the surface of a workpiece to automatically follow the surface irregularities. The method and apparatus operates to follow a virtual control surface located below the actual surface of the workpiece thereby allowing the irregular topography surface to be uniformly processed with closed loop process control.

Abstract: A method for providing a surface treatment along the surface of a work piece, using a burnishing tool having a tool head comprising a bearing for supporting a rolling element and an encasement for supporting the bearing. The bearing is formed from a polymer or polymer resin such as, but not limited to, polytetrafluoroethylene based resin, ultra-high-molecular-weight polyethylene based resin.

Abstract: A method and apparatus for improving the fatigue and stress corrosion cracking performance of irregular surfaces, such as welds assemblies of components, using a positioning system, such as a robotic or CNC machine, to position a tool head for inducing compression along and into the surface of a workpiece to automatically follow the surface irregularities. The method and apparatus operates to follow a virtual control surface located below the actual surface of the workpiece thereby allowing the irregular topography surface to be uniformly processed with closed loop process control.

Abstract: A burnishing tool and method for providing a surface treatment along the surface of a work piece, the burnishing tool having a tool head comprising a bearing for supporting a rolling element and an encasement for supporting the bearing. The bearing is formed from a self-lubricating polymer such as, but not limited to, polytetrafluoroethylene based resin, ultra-high-molecular-weight polyethylene based resin.

Abstract: A method for preventing or arresting the development and propagation of cracks in the material surrounding a fastener. The method includes introducing compressive residual stresses in the material surrounding the fastener. The compressive residual stresses offset the high residual tensile and applied stresses which the material may be subjected to in operation and thereby prevent or arrest the development of cracks. Using the output of a sensor, the surface treatment apparatus is positioned relative to a fastener. A compression tool is impinged against the surface of the material adjacent to the fastener and rotated around the perimeter of the fastener thereby inducing a zone of compressive residual stress.

Abstract: A work holder capable of measuring the amount of distortion occurring in a part as the part is machined, processed, treated, or otherwise operated upon and methods of using the same for quality control and process monitoring purposes. Indirect measurement of the distortion occurring in the part eliminates the need to individually strain gauge each part.

Abstract: A metallic article with improved fatigue performance and resistance to corrosive attack and stress corrosion cracking is produced by treating a first area of a metallic article with a first surface treatment that induces a specified amount of cold work. A second, sacrificial area of the metallic article in electrical communication with the first area is treated with a second surface treatment that induces an amount of cold work higher than that of the first surface treatment. Due to the differences in cold work resulting from the different surface treatments, the second area of the metallic article is less noble than the first area and is therefore more susceptible to corrosive attack. As a result, the second sacrificial area will preferentially corrode leaving the first area protected from corrosive attack. Compressive residual stresses induced in the surface of the metallic article through the surface treatments improve the fatigue performance and resistance to stress corrosion cracking.

Abstract: A method and an apparatus for performing the method of inducing compressive residual stress in blading members integrally formed with a rotor. The method includes using a caliper-type burnishing tool such that the caliper arms of the tool are contoured and oriented for placing the burnishing elements on opposite sides of the blading member to be treated. The blading member is burnished to introduce a pre-determined pattern of residual compressive stresses in a selected area of the blade.

Abstract: A metallic article with improved fatigue performance and resistance to corrosive attack and stress corrosion cracking is produced by treating a first area of a metallic article with a first surface treatment that induces a specified amount of cold work. A second, sacrificial area of the metallic article in electrical communication with the first area is treated with a second surface treatment that induces an amount of cold work higher than that of the first surface treatment. Due to the differences in cold work resulting from the different surface treatments, the second area of the metallic article is less noble than the first area and is therefore more susceptible to corrosive attack. As a result, the second sacrificial area will preferentially corrode leaving the first area protected from corrosive attack. Compressive residual stresses induced in the surface of the metallic article through the surface treatments improve the fatigue performance and resistance to stress corrosion cracking.

Abstract: The present invention relates to a surface treatment apparatus and method for inducing compressive residual stress in the surface of a workpiece with dimensional variations. The method comprises the acts of measuring the dimensions of the workpiece during a surface treatment operation and adjusting the surface treatment process parameters to account for the measured dimensions. In one embodiment, the apparatus comprises two surface treatment elements oriented in opposition to one another in a caliper configuration. The surface treatment elements are positioned and impinged against the surface of a workpiece by an actuator controlled by a computer control unit. The depth to which the surface treatment elements are impinged is precisely controlled to achieve the desired magnitude and depth of compressive residual stress. A sensor operatively connected to the apparatus senses and relays the dimensions of the workpiece to a computer control unit that adjusts the operating parameters accordingly.

Abstract: A work holder capable of measuring the amount of distortion occurring in a part as the part is machined, processed, treated, or otherwise operated upon and methods of using the same for quality control and process monitoring purposes. Indirect measurement of the distortion occurring in the part eliminates the need to individually strain gauge each part.

Abstract: A metallic article with improved fatigue performance and resistance to corrosive attack and stress corrosion cracking is produced by treating a first area of a metallic article with a first surface treatment that induces a specified amount of cold work. A second, sacrificial area of the metallic article in electrical communication with the first area is treated with a second surface treatment that induces an amount of cold work higher than that of the first surface treatment. Due to the differences in cold work resulting from the different surface treatments, the second area of the metallic article is less noble than the first area and is therefore more susceptible to corrosive attack. As a result, the second sacrificial area will preferentially corrode leaving the first area protected from corrosive attack. Compressive residual stresses induced in the surface of the metallic article through the surface treatments improve the fatigue performance and resistance to stress corrosion cracking.

Abstract: A method and system for designing a part with improved fatigue life and resistance to stress corrosion cracking in which residual stresses existing in the part are accounted for. The performance criteria and operating conditions of the part are assessed and a total stress state is determined from the sum of the residual stresses and applied stresses acting on the part. Unified Fatigue Performance Model or Smith-Topper-Neuber parameters are used to determine fatigue life functions which, in turn, are used in conjunction with a fatigue design diagram to determine the appropriate residual stress to introduce in order to optimize the part's resistance to stress induced failure mechanisms. A residual stress distribution is then designed to avoid distortion of the part while still imparting the beneficial effects of compressive residual stress.

Abstract: This invention relates to a method and an apparatus for performing the method of inducing compressive residual stress along the surface of a part. In the preferred embodiment of the invention, the method includes burnishing or deep rolling a surface using a first and a second roller or ball burnishing members, whereby the first and second burnishing members may have a different diameter and/or modulus of elasticity. In another preferred embodiment of the invention, the burnishing operations may be performed while the surface of the part is at different temperatures.

Abstract: The present invention is a novel method for reducing tensile zones in the surface of a part comprising the steps of selecting a region of the part to be treated and programming a control unit of a burnishing apparatus to perform a burnishing operation, the burnishing operation being performed such that the density of burnishing and the magnitude of compression are varied to reduce the high tensile stress along the boundaries of the selected region. In a preferred embodiment of the invention the burnishing operation induces a deep layer of compression within the surface having associated cold working of less than about 5.0 percent.

Abstract: The present invention is a novel method and an apparatus for implementing the method of inducing a layer of compressive residual stress along the surface of a part comprising the steps of selecting a region of the part to be treated; selecting the magnitude of compression and the residual stress distribution to be induced in the surface of the selected region of the part; exerting pressure against the surface of the selected region, the pressure being applied in a selected pattern along the surface to form zones of deformation having a deep layer of compressive stress; and varying the pressure being exerted against the surface to produce the desired residual stress distribution and magnitude of compression within the surface.

Abstract: The present invention is a novel method and an apparatus for implementing the method of inducing a layer of compressive residual stress along the surface of a part comprising the steps of selecting a region of the part to be treated; selecting the magnitude of compression and the residual stress distribution to be induced in the surface of the selected region of the part; exerting pressure against the surface of the selected region, the pressure being applied in a selected pattern along the surface to form zones of deformation having a deep layer of compressive stress; and varying the pressure being exerted against the surface to produce the desired residual stress distribution and magnitude of compression within the surface.